1. Field of the Invention
An object of the present invention is a method for the 3D encapsulation of semiconductor chips, each of the chips containing, for example, an electronic component, an integrated circuit or a sensor, this encapsulation being designed to display efficient heat dissipation or removal by conduction.
2. Description of the Prior Art
The making of current electronic systems, for both civilian and military use, should take account of increasingly greater requirements of compactness owing to the constantly rising number of circuits that are being implemented.
In this search for greater compactness, it has already been proposed to make 3D stacks of integrated circuits as is described, for example, in the U.S. Pat. No. 4,706,166. According to this embodiment, the chips are positioned on a printed circuit, against one another perpendicularly to the printed circuit. The connection pads or contacts of each of the chips are brought to one and the same border region of the chip. This side is positioned on the printed circuit, and the connections with the printed circuit are made thereon. However, this arrangement has limitations, related notably to the number of pads that it is physically possible to place on only one side of a semiconductor chip. In addition, this arrangement is costly because the chips are not standard ones (the arrangement of the pads has to be modified). Furthermore, there is little access possible to the connections thus made and, in addition, these connections cannot be seen: this limits their use. Finally, in certain applications, a problem of heat dissipation may arise. Conventionally, this heat dissipation may be achieved by conduction or by convection. In the embodiment described here above, heat dissipation by conduction is limited owing to the fact that it can be done only by the pads providing the electrical connection to the printed circuit, these pads having a small section and being limited in number. To work satisfactorily, therefore, a device such as this has to be cooled by convection. However, in certain applications, cooling of this type is difficult and even impossible to implement, notably in avionic or space applications.